Substrate composition for sequestration of skin irritants

Details Substrate composition for sequestration of skin irritants Substrate composition for sequestration of skin irritants

1999-12-29

2003-02-18

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Wearing apparel, fabric, or cloth

C424S401000, C424S443000, C424S400000, C424S078080

Reexamination Certificate

active

06521241

ABSTRACT:

BACKGROUND OF THE INVENTION
The stratum corneum is the superficial cornified layer of the skin that provides a barrier to water evaporation and, as such, is essential for terrestrial life. In addition to preventing water loss, the stratum corneum also reduces the permeation of undesirable molecules from the external environment. The stratum corneum consists of dead cells (comeocytes) embedded in a lipid-rich (fatty-acid, ceramide, cholesterol) matrix. Both the corneocytes and the intracelluar lipids are derived from epidermal keratinocytes. This structure of corneocytes embedded in lipids have given rise to a brick (corneocytes) and mortar (lipids) model of stratum corneum structure and function. It is thought that much of the barrier properties of the skin can be attributed to this structure. Substances deposited on the skin must traverse this structure through a tortuous path to gain access the underlying viable layers of the skin. Substances that are irritating to the skin often initiate an elaborate cascade of immunological events once they contact viable skin cells. These events ultimately lead to skin inflammation.
In particular, nasolabial skin is more vulnerable to skin irritation than many other sites on the body. This vulnerability is due to the decreased barrier function of nasolabial skin relative to other body sites. The rate of water loss through the skin can be measured and is indicative of the barrier properties of the skin
12
. A low level of water loss through the skin is normal. Movement of water through the skin is often referred to as Transepidermal Water Loss (TEWL) and is typically expressed as g∝M
−2
∝hr
−1
. TEWL readings are routinely used to determine the barrier properties of a skin site at any given point in time
13
. Normally, significant differences in TEWL values can be found between disparate anatomical sites
14
. Studies have shown that the barrier properties of facial skin are significantly lower than other sites on the body. Indeed, differences in barrier properties between various sites on the face itself have been observed
14,15
. Indeed, the TEWL values obtained for nasolabial skin were among the highest values obtained on the face. With few exceptions, it appears that the face, and more specifically, nasolabial skin, has the lowest barrier properties of any skin site on the human body.
The barrier function of the skin with regard to moisture barrier, as measured by TEWL, often correlates with the skin's ability to exclude exogenous substances as well
14,16
. As the barrier to water decreases (increasing TEWL value) exogenously applied molecules are often more likely to penetrate to the viable layers of the skin
12
. This suggests that nasolabial skin may be more permeable to topically applied irritants and therefore more susceptible to inflammation relative to other skin sites.
Skin barrier function can be compromised by a variety of insults. Examples of treatments known to diminish skin barrier function include, but are not limited to, physical treatments (abrasion, tape stripping, ultrasonics, electrical fields), enzymes, solvents, surfactants, and elevated ambient humidity
17,18,19,20,21,22,23
. Repeated wiping of nasolabial skin with facial tissue can diminish skin barrier function due to abrasion. Insults that diminish skin barrier function can predispose skin to inflammatory events by the enhanced uptake of irritants through the stratum corneum.
Bodily fluids may contain skin irritants. For example, the nasal secretions of individuals experiencing colds or allergies contain a myriad of substances that can potentially irritate nasolabial skin. These substances include, but are not limited to, an array of biologically active components including cytokines, eicosanoids, enzymes, and various toxins. For example, the cytokines interleukin-1&bgr; (IL-1&bgr;) and interleukin-8 (IL-8) are present in high concentrations in nasal secretions
1,2,3
. Likewise, the eicosanoids leukotriene B
4
(LTB
4
) and prostaglandin E
2
(PGE
2
) are also present at high concentrations in nasal secretions
4,5,6,7,8
. Additionally, the enzymes kinase, tryptase, phospholipase, and glycosydase are present in nasal secretions. Finally, nasal secretions can contain superantigens produced by the bacterium
Staphylococcus aureus
including staphylococcal enterotoxins A (SEA), B (SEB), and Toxic Shock Syndrome Toxin-1 (TSST-1) as well as other bacterial by-products. Furthermore, the cutaneous responses to topically applied cytokines, eicosanoids, enzymes, and superantigens have also been described
9,10,11
.
Enzymes commonly found in other biological fluids, particularly proteases and lipases in feces, are known to damage skin barrier function and cause skin inflammation. For example, prolonged exposure of the skin to fecal proteases and lipases is thought to be a major cause of skin damage that leads to diaper dermatitis in infants. The care of skin in individuals with ostomies is difficult due to the frequent contact of digestive enzymes with skin surrounding the ostomy. These enzymes can degrade skin proteins and lipids and cause irritation of the skin. Bodily fluid enzymes can also cause or exacerbate psoriasis.
Therefore, bodily secretions contain a variety of irritants that can initiate skin inflammation. In addition, physical contact with other animals and plants can confer skin irritants to an individual, such as from poison ivy. Furthermore, other caustic inanimate materials, such as acidic chemicals, can cause skin irritation.
What is needed in the art today are novel mechanisms for preventing or mitigating skin inflammation due to the exceedingly complex mixture of irritants in bodily secretions and the environment.
A number of approaches are known for protecting the skin against the action of skin irritants. Examples include protective apparel, skin protectant formulations, and anti-inflammatory compositions.
Barrier compositions can provide demonstrable clinical benefits. However, it is known that while many compositions can retard the penetration of one type of irritant it may not afford a similar level of protection against others
24,25
. This evidence suggests that many currently available skin protectant formulations are unable to exclude a wide range of irritants that differ based on hydrophobicity, size, and/or chemical composition. Consequently, many skin protectant formulations may not provide adequate protection against a complex mixture of skin irritants.
Another method of addressing skin irritation due to contact with skin irritants is the use of anti-inflammatory compounds. The topical use of anti-inflammatory compounds does not protect the skin from coming in contact with an irritant. Instead, for many skin irritants, damage to the skin still occurs but the inflammatory response is mitigated by the anti-inflammatory substance. Therefore, the effect of anti-inflammatory compounds is exerted by influencing the biology of viable skin cells rather than by preventing the skin damage that elicits the inflammatory event in the first place.
PCT publication WO 97/38735 teaches the use of a singular sequestrant (organophilic clays; i.e. clays modified with hydrophobic substances), such as quarternium-18 bentonite, to absorb and deactivate fecal proteolytic enzymes to prevent diaper rash of the skin. A diaper fabric incorporating the organophilic clay dispersed in a super absorbent polymer is suggested, as well as other pharmaceutically suitable vehicles for the organophilic clay, such as lotions, emulsions, creams, gels, and aqueous vehicles. The reference teaches that compounds having C-8 and longer hydrocarbon chains should be excluded from the composition. The protective composition is specifically intended to act as a barrier to prevent fecal enzymes from contacting the skin. Further, lotions and aerosols containing organophilic clay, ion exchanged with a quaternary ammonium compound, are used to block and absorb plant allergens in U.S. Pat. Nos. 5,017,361 and 5,702,709. Additionally, art exists to describe the inclusi

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